How Useful Is Pulse Rate?

[belscb]

All else being equal, a higher metabolic rate will mean a higher pulse, apparently somewhere around 85 beats/minute for an adult during the day (lower pulse in the morning due to cortisol, etc.). I understand this, and it makes sense. But what if all else is not equal? In particular, it seems there might be two complicating factors here:

VO2 max - my understanding is that certain types of exercise can increase an individual's ability to efficiently absorb and transport oxygen. Is this true? If so, then theoretically wouldn't an active individual with a greater VO2 max require a lower resting pulse than a more sedentary individual, all else being equal?

CO2 saturation - according to Dr Peat and Dr Buteykom, increased CO2 can decrease pulse rate because "relaxes the blood vessels so it decreases peripheral resistance and that makes the heart able to pump more blood more easily with less work. So it usually means a bigger stroke volume [...] your heart doesn't have to work so frantically."

So what's the deal? It seems like a healthy, athletic person (higher VO2 max) who also has high CO2 levels could conceivably have a very low pulse. So in that case would a low pulse *not* be a warning sign of a low metabolism?

 

[yerrag]

Your question is predicated on the idea, I think, that our body will produce energy up to a certain maximum level. And that when the production of energy is so efficient that the max has been reached, a person with more efficient energy production will require less effort to produce that much energy, whereas a person with less efficient metabolism would require more. So, the former will have a lower heartbeat than the letter. And that makes sense, except...

... that that assumption could be faulty.

Ray Peat talks about the use of surplus energy in the body for development. The surplus energy could be used to further develop the brain, or it could also be used for improving physical characteristics in the form of better musculature, or better skin, or a bountiful mane. If we think of our body as a sink for energy that has no limits, the engine that makes provides this energy would not have an easily defined maximum limit of energy production.

I used to think that if I have the right body temperature, at 37C, and if my resting heart rate is at 65, I should be happy thinking that I am more efficient than a person with the same body temperature, but has a higher heart rate at 85. But it may just be that my engine has some constraints that are limiting the heart rate to 65. What if the other guy has a higher heart rate that allows him to produce more energy, and that he has a surplus of energy that allows him to regenerate more the cells in his internal organs, and that this continual regenerative ability allows him to age less? We may never know.

 

[belscb]

I'm not denying the relationship to energy production. I'm simply not sure how that relates to (a) the absorption of O2/CO2, and also (b) the efficiency of circulation. Those are both different than energy production per se. Even Ray Peat himself says that increased CO2 will reduce pulse by increasing the efficiency of circulation. The tricky thing is though, pulse seems to be related to all three factors: energy production, O2/CO2 absorption, and efficiency of circulation. The first would increase pulse, but it seems the latter two would decrease pulse. So what is a healthy pulse, really? How useful is this metric?

 

[yerrag]

I'm not denying the relationship to energy production. I'm simply not sure how that relates to (a) the absorption of O2/CO2, and also (b) the efficiency of circulation. Those are both different than energy production per se. Even Ray Peat himself says that increased CO2 will reduce pulse by increasing the efficiency of circulation. The tricky thing is though, pulse seems to be related to all three factors: energy production, O2/CO2 absorption, and efficiency of circulation. The first would increase pulse, but it seems the latter two would decrease pulse. So what is a healthy pulse, really? How useful is this metric?

If someone says he is so healthy that his pulse is at 40, would you agree with him?

If someone says he is because his heart rate is 95, would you?

And if yours is at 65, what would you say about your health?

It is an indicator, but in itself it is meaningless. You need other markers to confirm.

But it's easy to get readings, even without an instrument except a watch. And some smartphones can take the reading easily.

If you were to get a starting estimate, this, along with temperature, is more useful than oftentimes going to a doctor and getting a lot of blood tests and scans, and being given a false negative or a false negative.

Is it perfect? No.